xr16m698 Exar Corporation, xr16m698 Datasheet - Page 20

• Manufacturer Part Number: xr16m698
• Description: 1.62v To 3.63v High Performance Octal Uart With 32-byte Fifo
• Manufacturer: Exar Corporation

XR16M698
1.62V TO 3.63V HIGH PERFORMANCE OCTAL UART WITH 32-BYTE FIFO
Each UART in the 698 includes the infrared encoder and decoder compatible to the IrDA (Infrared Data
Association) version 1.0. The input pin ENIR conveniently activates all 8 UART channels to start up in the
infrared mode. Note that the ENIR pin is sampled when the RST# input is de-asserted. This global control pin
enables the MCR bit-6 function in every UART channel register. After power up or a reset, the software can
overwrite MCR bit-6 if so desired. ENIR and MCR bit-6 also disable the receiver while the transmitter is
sending data. This prevents echoed data from reaching the receiver. The global activation ENIR pin prevents
the infrared emitter from turning on and drawing large amount of current while the system is starting up. When
the infrared feature is enabled, the transmit data outputs, TX[7:0], would idle at logic zero level. Likewise, the
RX [7:0] inputs assume an idle level of logic zero.
The infrared encoder sends out a 3/16 of a bit wide HIGH-pulse for each “0” bit in the transmit data stream.
This signal encoding reduces the on-time of the infrared LED, hence reduces the power consumption. See
Figure 10
The infrared decoder receives the input pulse from the infrared sensing diode on RX pin. Each time it senses a
light pulse, it returns a logic zero to the data bit stream. The decoder also accepts (when FCTR bit-4 = 1) an
inverted IR-encoded input signal. This option supports active LOW instead of normal active HIGH pulse from
some infrared modules on the market.
2.14
Infrared Mode
below.
F
IGURE
10. I
Receive
IR Pulse
(RX pin)
RX Data
TX Data
Transmit
IR Pulse
(TX Pin)
NFRARED
T
0
RANSMIT
Bit Time
Bit Time
0
1
1/16 Clock Delay
1
D
0
ATA
0
1
E
Character
Data Bits
NCODING AND
1
0
20
3/16 Bit Time
Data Bits
Character
0
0
0
1
R
1 1
1
ECEIVE
0
0
D
1/2 Bit Time
ATA
1
1
IRdecoder-
D
IrEncoder-1
ECODING
REV. 1.0.0